Data from Lionel Wiener, Articulated Locomotives (1930); and "New Zealand Government Railway-Design 1134", Beyer-Garrrat Patent Articulated Locomotives (Manchester, England: Beyer-Peacock & Company Limited, 1931), archived on flickr's Historical Railway Images at [], et seq, p. 53. .. See also "New Zealand's Latest Locomotive", New Zealand Railways Magazine, Volume 12, Issue (1 November 1937), archived at [
], last accessed 24 February 2019.
Wiener noted that these Double Pacific locomotives were intended to work main-line passenger service at a maximum speed of 50 mph (80 kph) and scale gradients of up to 2.5%. To gain that kind of power, the designers went to a three-abreast cylinder layout using a maximum cutoff of 50% in a Garratt layout of two engine units pivoting under the ends of a centrally mounted boiler and firebox. In the G class, however, the cab and fuel bunker were permanently joined and the round-topped firebox was radially stayed.
The boiler was relatively large at 78" diameter, further evidence of the Garratt layout's ability to grant high capacity to railroads with tight clearances and light rail. The firebox had two Nicholson thermic syphons. Outside valve gears were actuated by Walschaerts and the inside motion came from Gresley conjugated gear. Maximum cutoff was 50%.
Brad, a New Zealand correspondent, adds this in response to a question:
"Quite simply the G's didn't have a career. They pulled huge trains in the north island from 1930-1936. They were then sent to the south island, where they were immediately rebuilt into six 4-6-2 loco's. Their huge power wasn't needed in New Zealand, and we replaced them with 4-8-4's. They spent most of the 30's up and down the Raurimu spiral. A 4-6-2 or a 4-8-4 would pull up on one side, The G coupled on, went around the spiral, then was uncoupled, ready for the next train. That's about all that I know."
Date: 9/13/1999 1:34:52 AM Eastern Daylight Time
From: otama@ihug.co.nz (brad)
The NZRM provided more details when it unveiled the Pacifics in 1937. The Garratts were just "too cumbersome ...where traffic requirements and restricted marshalling yards and crossing loops prevented full use." They also were too large for hand-firing while the automatic stoker fitted "proved unsuitable for use with New Zealand coal, since the coal mines in New Zealand and Australia are not equipped with machinery to grade coal to regular size."
Principal Dimensions by Steve Llanso of Middle Run Media | |
---|---|
Class | G |
Locobase ID | 705 |
Railroad | New Zealand Government Railways |
Country | New Zealand |
Whyte | 4-6-2+2-6-4 |
Number in Class | 3 |
Road Numbers | 98-100 |
Gauge | 3'6" |
Number Built | 3 |
Builder | Beyer, Peacock |
Year | 1928 |
Valve Gear | Walschaert |
Locomotive Length and Weight | |
Driver Wheelbase (ft / m) | 21.50 / 6.55 |
Engine Wheelbase (ft / m) | 50.83 / 15.49 |
Ratio of driving wheelbase to overall engine wheelbase | 0.42 |
Overall Wheelbase (engine & tender) (ft / m) | |
Axle Loading (Maximum Weight per Axle) (lbs / kg) | 33,376 / 15,139 |
Weight on Drivers (lbs / kg) | 196,004 / 88,906 |
Engine Weight (lbs / kg) | 326,368 / 148,038 |
Tender Loaded Weight (lbs / kg) | |
Total Engine and Tender Weight (lbs / kg) | |
Tender Water Capacity (gals / ML) | 4000 / 15.15 |
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) | 6.70 / 6.10 |
Minimum weight of rail (calculated) (lb/yd / kg/m) | 54 / 27 |
Geometry Relating to Tractive Effort | |
Driver Diameter (in / mm) | 57 / 1448 |
Boiler Pressure (psi / kPa) | 200 / 1380 |
High Pressure Cylinders (dia x stroke) (in / mm) | 16.5" x 24" / 419x610 (6) |
Tractive Effort (lbs / kg) | 58,462 / 26517.95 |
Factor of Adhesion (Weight on Drivers/Tractive Effort) | 3.35 |
Heating Ability | |
Tubes (number - dia) (in / mm) | 222 - 1.75" / 44 |
Flues (number - dia) (in / mm) | 43 - 5.25" / 133 |
Flue/Tube length (ft / m) | 12 / 3.66 |
Firebox Area (sq ft / m2) | 266 / 24.71 |
Grate Area (sq ft / m2) | 58.30 / 5.42 |
Evaporative Heating Surface (sq ft / m2) | 2223 / 206.52 |
Superheating Surface (sq ft / m2) | 542 / 50.35 |
Combined Heating Surface (sq ft / m2) | 2765 / 256.87 |
Evaporative Heating Surface/Cylinder Volume | 124.76 |
Computations Relating to Power Output (More Information) | |
Robert LeMassena's Power Computation | 11,660 |
Same as above plus superheater percentage | 13,992 |
Same as above but substitute firebox area for grate area | 63,840 |
Power L1 | 8990 |
Power MT | 606.71 |